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246 Cards in this Set
- Front
- Back
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One astronomical unit is |
The distance from the earth to the sun, a measure of distance |
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One lightyear is |
the distance light will travel in a year, a measure of distance |
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A Scientific Theory must be |
must be testable
must be repeatedly tested simple and elegant |
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Occam's Razor |
The Simplest explanation is the truest one |
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What is the speed of light? |
300000m/s or 3 * 10^8 |
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What is a fact |
an objective and verifiable observation |
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What is a Hypothesis |
an educated guess that you can test |
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What is a theory |
A framework of ideas that are used toexplain a set of observations. It has beenrigorously tested.
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What is a Law? |
a Detailed description of how somethinghappens (does not tell us why somethinghappens). usually assoc with math
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What is the Ecliptic? |
is a tilted axis on which the sun travels within the celestial sphere |
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What is the angle of the ecliptic? |
23.5 |
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Stars appear to move |
East to West |
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What is a siderial day? |
the time it takes the Earth to returnto the same orientation in space relative tothe stars (true rotation period)
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What is a solar day |
- time it takes from one noon to thenext.
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Which is longer, the solar or siderial day? |
The solar day by 4 minutes, because it has to rotate slightly further to face the sun |
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What is responsible for the seasons? |
The earths tilt |
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The earth's tilt does what |
Precesses every 26000 years, like a top |
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How much of the moon can we see |
the same side |
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How long is the moons orbit |
27days |
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How long and what is a Synodic |
29.5 days to complete a full cycle of moon phases |
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What are the phases of the moon starting at the beginning of the cycle |
New Moon Waxing Crescent first quarter Waxing Gibbous full moon Waning Gibbous Third Quarter Waning Crescent |
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Stellar Paralax is essentially |
Trianglulation trig |
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A Parsec (pc) is a measure of |
distance |
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What is retrograde motion |
when planets appear to move west to east instead of east to west, backwards in the sky, for a short period of time |
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Geocentric model |
earth centered Aristotle required epicycles (small circles) to explain planetary movement the main orbital plane is called the deferent |
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Heliocentric model |
sun centered Aristarchus measured angular sizes of the sun and moon |
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Copernican model |
earth is not center the motions of the sun in the sky are actually the movement of the earth Planets orbit sun in PERFECT CIRCLES |
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Galileo Galilei discovered which things that disproved geocentric perfectionism and supported Copernicus |
peaks and valleys on the surface of the moon sun spots 4 moons of jupiter phases of venus |
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What was special about Jupiters moons |
they proved that not everything orbited the earth |
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Keplers 1st law |
The orbital paths of the planets are elliptical(not circular) with the Sun at one focus. |
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Keplers 1st law terms |
major axis= x axis rep by a minor axis = y axis rep by b (semi half of above) Perihelion= the closest the sun will be to earth Aphelion= the furthest the sun will be from earth eccentricity |
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Eccentricity |
how elliptical a shape is. bigger e = more elliptical. Represented by e. the e of a circle is 0 |
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What is the Perihelion formula |
perihelion = a(1-e) |
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what is the aphelion formula |
Aphelion= a(1+e) |
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Keplers 2nd law |
A planet in its orbit sweeps out equal areasof the ellipse in equal intervals of time.
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When area and therfore time intervals are equivalent, how is velocity determined? |
the distance travelled, small d = slow, big d =fast |
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When are planets fastest? |
when furthest from the sun |
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Keplers 3rd law |
The square of a planet’s orbital period isproportional to the cube of its semimajoraxis.
essentially a formula |
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Newtons 1st law (law of inertia) |
An object at rest stays at rest unless actedupon by an outside force. An object inmotion stays in motion, unless acted uponby an outside force.
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what is inertia |
Inertia is the resistance of an object to changeits motion. |
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newtons 2nd law |
When a force, F, acts upon a body of mass m, it imparts an acceleration equal to the force divided by the mass F=ma |
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Newtons 3rd law |
For every action, there is an equal and opposite reaction i.e. you push me I push back |
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Gravity is |
always an attractive force felt by all objects in the universe |
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Fgrav = GM1M2/ r^2
r is what |
the distance of separations |
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Escape velocity is the |
Amount of velocity needed to escape a gravatational field |
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Electromagnetic radiation EMR |
Energy is transmittedthrough space from one point to another in theform of rapidly fluctuating electric and magneticfields. |
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EMR is produced by |
accelarating e- |
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All EMR travels at |
the speed of light |
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Frequency:
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The number of wave crests thatpass a point every second (measured inHertz, Hz).
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Period:
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Time it takes for a wave to repeatitself (measured in seconds, s).
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Wavelength (λ):
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the distance between twosuccessive points on the wave (normally crest tocrest). Measured in metres (m).
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Velocity (v):
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the speed at which the wave ismoving. Measured in metres per second (m/s) |
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Formula for EMR velocity |
v=fλ |
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frequency and wave length are |
Inverse values f= 1/λ λ =1/f |
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what does c stand for |
the speed of light, of all EMR |
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Order EMR from biggest λ to smallest |
Radiowaves Microwaves Infra-red visible Ultra-violet Xrays Gamma Rays |
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What is the λof the visible spectrum from biggest to smallest (red to violet) what are the f |
400 - 700 nm (nanometers) 4*10^14 - 7.9*10^14 hz |
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What rays does our atmosphere allow in? |
Radio waves/ visible light |
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Absolute 0 is |
0K where all thermal motions cease |
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The Blackbody curve is |
A idealistic mathematical representation of a celestial object that emits and absorbs all radiation |
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The Blackbody spectrum, the radiation emitted depends entirely on |
its temperature |
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The peak of a blackbody curve |
is the colour/type of radiation emitted the most |
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Weins law |
The peak wavelength of radiation(of the blackbody curve) can be found it wemeasure the temperature in Kelvins
or 2.9 = λmax x T |
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Stefan’s Law:
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Flux (energy/area) is equal to Temperature to the power of 4 F=oT^4 |
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The Doppler effect definition |
The apparent change in thefrequency (or wavelength) of a wave caused bythe relative motion of the source of the wave andthe observer. |
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Doppler effect colours |
Objects moving towards you appear blue shifter objects moving away from you appear red shifted adjacent objects are unaffected |
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How does the doppler effect affect wave lengths? |
Moving towards the source of radiation,wavelengths seem shorter (larger frequencies);moving away, wavelengths appear longer(smaller frequencies) |
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Positive doppler # are |
Red shifted/ moving away |
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WHat is a specrograph |
A simple tool that separates light into its different wavelengths |
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Three types of Spectra |
continuous absorption emission |
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Continuous spectrum |
A luminous solid or liquid, or a sufficientlydense gas, emits light of all wavelengths andso produces a continuous spectrum ofradiation.
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Emission line Spectrum |
A low-density, hot gas emits light whosespectrum consists of a series of bright emissionlines
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Absorption line spectrum |
A cool, thin gas in front of a continuousspectrum will absorb certain wavelengths andproduce a dark line or absorption linespectrum.
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These deinitions are |
Kirchhoff’s laws |
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An atom has multiple energy levels. What are the called in order of closest to nucleus |
Ground state (n=1) first excited state (n=2) second excited state (n=3) third excited state (n=4) Ionization |
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the ionizationenergy |
is the maximum energy that an electron can absorb beforeit is no longer bound to the atom |
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The amount of light energy absorbed or emitted by an e- changing orbitals must
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correspond exactly to the energy difference betweentwo orbitals. |
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Photons |
are particles of light emitted by jumping e- they contain the energy released |
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An e- that absorbs a photon |
jumps to a higher energy state |
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When an e- jumps to a lower energy state is |
emits a photon |
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The energy of a photon |
corresponds to theenergy difference between the two energystates (or orbitals).
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e- want to be |
in the lowest possible states |
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How are spectral lines formed |
Atoms absorb photons of agiven energy in their atmospheres whichcorresponds to a particular wavelength.
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These absorption lines are
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unique, like a fingerprint and correspond to an elemet |
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Spectral lines tell us |
Chemical composition (already discussed)
• Temperature • Radial velocity (Doppler effect) • Line broadening (thermal, rotational) • Magnetic fields (not required) |
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Lenses _____ incoming light, mirrors ____ incoming light |
bend/refract reflect |
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Snell’s Law)
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Angle of incidence = angle ofreflection/refraction
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A converging lens |
directs incoming light to a focus |
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Curves mirrors |
direct incoming light to a focus |
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The focal length is |
how far the reflective/refractive surface is from its focuas |
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3 types of telescopes |
1.Optical Telescopes 2. Radio Telescopes 3. Space Telescopes |
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The telescope was invented by Hans Lippershey but made famous by |
Galileo who build a refracting telescope and looked at the sky |
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A refracter telescope uses |
a lens to bend light and bring it into focus |
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Newton invented |
reflector telescopes with mirrors |
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Prime focus telescope |
uses only one mirror and the focus is back out the top of the tube |
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Newtonian focus telescope |
uses two mirrors to direct light out the side eye piece near the top |
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The Cassegrain focus |
Uses two mirrors (one broken) do direct light of the bottom of the tube |
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Nasmyth focus |
uses three mirrors to direct light out the side eyepiece near the bottom |
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What makes a good telescope |
Light gathering power Resolving power magnification |
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Light Gathering power |
how big the bucket is to collect light the larger the area the fainter the objects that can be observed |
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The observed brightness of an object is |
Proportional to the area of the mirror or the square of the Diameter |
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Resolving power |
Resolution the ability to distinguish fine details |
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Magnification |
the least important factor magnification is determined by focal length. a telescopes purpose is to collect light, not to magnify |
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How astronomers record data |
drawing photographic plate 5% efficient CCD or Charge coupled device 80-90% efficient |
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The invention of computers |
allow astronomers to use many smaller mirrors to make one single image |
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the E-ELT |
the european extremely large telescope ~40m in diameter |
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Where do you build telescopes? |
High Altitude (above clouds and through less atmosphere turbulance) Dry desert (water effects infrared radiation) desolate (far from light pollution) |
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Atmospheric seeing (blurring) |
atmospheric turbulance changes in temp and density distort light |
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adaptive optics |
deforms the shape of the mirrorto match the incoming atmospheric wavefront
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Radio telescopes |
are large due to large wave lengths can observe day or night unaffected by dust unaffected by atmospheric turbulance |
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Interferometry |
using multiple telescopes (radio) to observe the same object in a greater resolution. the distance between the dishes = baseline which is essentially the diameter of the combined telescope. |
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Because of their large size, radio telescopes |
have the smallest resolution so they user interferometry |
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The Hubble is |
a space telescope |
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deep field observation
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is one that spends along time looking at a single patch of space,collecting as much light as possible.
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Why put telescope in space |
because they do notneed to look through the Earth’s atmosphere.• In space, telescopes are able to observe the entire EM spectrum |
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X Ray astronomy |
X-rays are very high energy (E=hƒ).As a result, they cannot easily be reflectedbecause they tend to pass through things.Use a series of nested, cylindrical mirrors todeflect the X-rays to a focus/point.CCDs do not work well for X-rays, so photons arecounted using electronic detectors.
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Name the layers of the sun |
Core Radiative zone convection zone photosphere chromosphere Corona |
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Density of the layers as we move towards the edge |
steadily decreasing |
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temp of the layers as we move towards the edge |
steadily cooling except for the corona which is extremely hot |
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Hydrostatic Equilibrium:
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The balance of theinward force of gravity with the outward pressure
like newtons 3rd law |
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High internal pressure leads to
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high central temperature, crucial for production of energy
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Solar oscillations
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the sun has internal pressure waves |
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helioseismology
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The study of the solar oscillations, as theyreflect off thephotosphere iscalled |
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Conveyor Belt:The MeridionalPlasma Flow
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Helioseismology allowedscientists to discover largescale global circulationpatterns.Circulates at about 15 m/sand takes about 40 years tocomplete one loop (four on the sun)
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Radiative Zone
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Gas is completely ionized i.e. no bound electronsto capture photons.Transparent to radiationHigh density, high temperature, high collision ratebetween atoms |
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Convective Zone |
Temperature decreases, fewer collisions, notcompletely ionized i.e. electrons are bound toatoms.The gas can now absorb the outgoing photonscoming from the radiative zone.Energy is therefore transported by convectionHotter, less dense gas rises |
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Granulation |
Direct result ofconvectionHot spots rising, coollines sinking |
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The Photosphere |
The line-forming regionBase of the photosphere is ~5800 K and isresponsible for the continuous spectrum(Blackbody curve).Temperature decreases outwards towards the topof the photosphereSpectral lines are formed at various depths |
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The sun is mostly made of |
helium and hydrogen |
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Chromosphere
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Tenuous lower atmosphere - low density, lowertemperatureDoesn’t emit a lot of light Can be observed during a solar eclipsePhotosphere is too bright and densities too low tobe able to see the chromosphere otherwise. |
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Spicules |
jets of hot matter being expelled intothe Sun’s upper atmosphere (~100 km/s)Tend to accumulate around the edges of supergranules |
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Corona |
Temperature increases - can be millions of KelvinCan be seen during an eclipseSpectrum changes from absorption to emission. |
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Solar Wind |
Hot coronal gas thatflows outward intospace (protons andelectrons; ~500 km/s)Continuallyreplenished frombelow.Sun loses about 2million tonnes/s |
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Sunspots |
Dark patches on the solar surface~10 000 km across, last 1-100 daysMagnetic field ~1000 times stronger thanaverage solar field |
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Zeneth |
when you look straight up whatever is directly above you |
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Circumpolar |
stars and constellatoions that can always be seen in the sky ie. little dipper and polaris |
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Do other planets have seasons |
yes! they all have their own tilt |
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for the first half of the moon cycle (waxing) (new to full) the moon can be seen in the sky ... |
chasing the sun across the sky |
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for the last half of the moon cycle (waning) (full to new) the moon can be seen in the sky |
being chased by the sun |
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Solar eclipse |
the moon is between the earth and sun |
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Lunar eclipse |
the moon is in the shadow of the earth |
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What is the ratio of conversion |
(what you want)/(what you have) = ( the ratio ie 1 radian / 206265") |
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when there is increase frequency there is _____ energy |
increased |
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if you increase the temp on a blackbody curve, the wave length |
decreses f increases |
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Stars produce what kind of spectrum? |
Absorption the cooler exterior of the star acts as the cool cloud of gas |
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The more you reflect the |
higher chance of losing light information |
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The shape of a mirror doesnt matter the |
area does |
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An effective theory must be |
continuously tested |
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The angular size of an object depends on which two qualities |
The objects actual size and its distance from us |
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What are constellations |
Groups of stars making an apparent pattern in the celestial sphere |
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On the earth where can you observe all stars in the sky over an entire year? |
the Equator |
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Where on earth would you have Polaris at your zenith? |
The North Pole |
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While watching a star, it moves 15 degrees across the sky. How long have you been watching it? |
1 hour 180 degrees of sky night for 12 hours = 15 degrees per hour |
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Four true statements about the ecliptic |
-It is tilted 23.5 degrees off the equator -The year is marked by the suns return to the same place among it -The sun appears to move 1 degree a day east -the major planets stay close to it, but not always on it |
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Which statement about the ecliptic is False? |
The moon can never leave it, but moves twelvetimes faster than the sun |
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When the sun rises, it is located in the constellation Gemini. When the sun sets later the same day it will be in |
the constellation Gemini |
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Night and day have approx equal length at qhat time or times of the year |
Vernal and Autumnal equinoxes |
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Characteristic of the spring equinox |
the sun rises due east today, but will rise slightly north of due east tommorow |
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Summer solstice characteristics |
-Longest day )most daylight) wof the yeat - the noontime sun reaches its highest point of the year |
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Fall equinox xharacteristics |
Thje sun has declination 0 degree today, but will have a negative declination tommorow |
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Winter Solstice Characteristics |
- the sunset occurs at its farthest point south of due west for the year -the noon time sun casts the longest shadoes - the sun crosses the meridian 23.5 degrees lower in altitude than the celestial equator |
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Parallax is |
inversely proportional to the distance to the star |
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A star with a large parallax |
Is a short distance from earth |
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Today the distances to the stars are measured by |
geometry |
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As the distance to the object increases Parallax |
decreases |
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As the size of baseline increases parallax |
increases |
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As the distance to the background objects , parallax |
remains the same |
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Consider the Moon and Sun. Their angular diameters are both equal to about .5 degree. If the Sun is roughly 400 times more distant than the Moon, how much bigger is the Sun’s diameter than the Moon’s?
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about 400x bigger |
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Keplers second law implies what about planetary motion |
A planet moves faster when it is closer to the sun |
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The greatest constribution of the greeks to modern thought was |
the development of scientific inquiry and model building |
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The major axis for a particular planet is known. In order to determine the perihelion and the aphelion, what other information about the planet is needed? |
The eccentricity of the orbit |
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Scientists today do not accept the ptolemaic model because |
The work of Tycho and kepler showd the heliocentric model was more accurate |
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on which of these assumption do ptolemy and Copernicus agree |
All orbits must be perfect circles |
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Which contribution to atronomy made by copernicus |
he laid out the order of and relative motion of the known solar system |
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The heliocentric model was first proposed by |
Aristarchus |
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It took centuries for the copernican model to replace the ptolemaic model because |
there was no scientific evidence to support either model until galileo |
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In Ptolemy’s Earth-centered model for the solar system, Venus’s phase is never full as viewed from Earth because it always lies between Earth and the Sun. In reality, as Galileo first recognized, Venus is __________. |
full whenever it is on the opposite side of the Sun from Earth, although we cannot see the full Venus because it is close to the Sun in the sky |
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if we could see it, at what time would full and new venus be highest in the sky? |
at noon |
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When would you expect to see Venus high in the sky at midnight?
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Never For Venus to be high in the sky at midnight, it would have to be on the opposite side of our sky from the Sun. But that never occurs because Venus is closer than Earth to the Sun. |
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Galileo. Which one provides evidence that Venus orbits the Sun and not Earth?
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We sometimes see gibbous (nearly but not quite full) Venus.
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a circular orbit would have the eccentricity of |
0 |
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according to keplars 3rd lae the square of the planets period in years is |
proportional to the cube of its semi major axis in AU |
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What does Keplars 3rd law imply about planetary motion |
Planets further from the sun orbit slower |
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If earths orbit around the sun were twice as large as now the orbit would take |
more than 2 x longer |
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Earth is located at one x of the moons orbit |
focus |
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According to keplars second law jupiter will be travelling most slowely around the sun at |
Aphelion |
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Earth orbits in the shape of a x around the sun |
ellipse |
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According to keplers 2nd law, pluto will be travelling fastest around the sun when at |
perihelion |
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the extent to which mars' orbit differs from a perfect circle is called |
eccentricity |
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What is not a characteristic of scientific theories |
They must be proven to the point that they will never be rejected or revised |
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Polaris will not always be the pole star due to |
precession shifting the celestial pole |
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The Ptolemaic model probably persisted for all these reasons
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-it explain why stellar parallax was not observed by the Greeks
-it had the authority of Aristotle behind it -it was consistent with the doctrines of the Catholic Church. -it used perfect circles, which appealed to geometry. |
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Was it possible for the geocentric system of Ptolemy to explain the observed retrograde motion of the planets?
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Yes, through a system of epicycles and deferents |
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What conclusion did kepler come to that revolutionized the heliocentric model |
Ellipses |
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the f of gravity between to objects |
Increases with the masses of the bodies but decreases with the square of the distances between them |
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According to Newton's Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would:
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decrease by 9 |
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how much stronger is the gravational pull of the sun on earth at 1AU than on Saturn at 10AU
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100x |
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Jupiter lies about 5AU from the sun, so at its distance |
the suns gravity is 25 times weaker than its pull on earth |
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Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton’s second law of motion _________
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the Moon has a larger acceleration than Earth, because it has a smaller mass
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What would happen to the orbits of each of the planets if the force of gravity was suddenly "turned off"?
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Each would move off in a different straight line.
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According to Newton, planets orbit in ellipses with what at the two foci?
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The center of mass and nothing
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A wave's velocity is the product of the:
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frequency times the wavelength of the wave.
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If a wave's frequency doubles, its wavelength:
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is halfved |
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what colour has the shortest wl? |
violet |
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what is constant for all EMR? |
velocity |
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tru or false |
false |
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EMR with wl of 700nm is |
red light |
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compared to UV, infrared radiation has a greater |
wl |
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If you throw a rock into a pond, it creates a wave in the water. What is responsible for creating an electromagnetic wave?
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a vibrating charged paerticle |
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Electromagnetic waves consist of co-oscillating electric and
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magnetic fields |
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the wave amplitudes are directed x to the directuion of the wave motion |
perpendicular |
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energy and information flows x to the wave motion |
parallel |
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stars with shorter wavelengths than the rest wave length are moving x us while the longer wavelengths are moving x us |
towards away from |
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As they are heated from low to high temperature, solid objects will appear to glow in which of the following sequences of colors
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Red, reddish-yellow, then white
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According to Wein's Law, if the surface temperature is increased by a factor of 2, its peak wavelength will:
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decrease by 2 |
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The total energy radiated by a blackbody depends on:
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the fourth power of its temp |
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Star A has a temperature 3 times that of star B. Both star A and star B are the same physical size. Which statement about star A and star B below is correct?
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Star A is bluer and brighter than star B.
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To see the Sun's hot corona (a temperature of 1,000,000 K), which part of the electromagnetic spectrum should one observe?
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the X-ray
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Alpha Centauri is observed to be reduced in wavelength (after correction for Earth's orbital motion) by a factor of 0.999933. What is the recession velocity (direction) of Alpha Centauri relative to the Sun?
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towards the sun |
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If a hydrogen atom encounters a photon of energy, what will its electron do?
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Absorb the photon only if it has the exact energy needed to move to another energy level
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Why are molecular lines more complex than elemental spectral lines?
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Molecules can vibrate and rotate as well.
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At these wavelengths, it is necessary to build telescopes with very large light-collecting x to obtain maps of sufficient sensitivity to faint cosmic signals
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area |
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in radio, it is necessary to build telescopes with very large signal-sensing x to obtain maps of sufficient detail.
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baselines
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Radio astronomers have pioneered the use of multiple telescopes working in concert that can produce maps of radio emission as detailed as optical images. These arrays of multiple telescopes are known as
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interferometers |
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Astronomical observations at these radio wavelengths can be obtained even during
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storms |
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What would you need to obtain a successful X-ray image of a high-energy source?
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A telescope designed and built to be launched into space.
A cosmic source of high temperature. |
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The Balmer Beta absorption line is a result of a transition of an electron in a hydrogen atom from:
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level 2 to level 4.
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In Bohr's model of the atom, electrons:
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only make transitions between orbitals of specific energies.
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The broadening of spectral lines can be caused by
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magnetic fields of the star.density of the hot medium.thermal motion of the hot atoms.rotation of the star.
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Spectral lines are often referred to as the stars' "fingerprints" because:
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fingerprints also consist of individual lines that make a pattern.both can be easily categorized.both are unique to their source.both are characteristic of the individual that produced them.
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Characteristics of reflecting telescopes |
most commonly used professionally today the hubble space tele worlds largest telescopes |
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Characteristics of refracting telescopes |
only up to 1m in diameter very lasge telscopes become top heavy incoming light passes through glass galileo's telescopes |
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The primary purpose of a telescope is to: |
collect a large amount of light and bring it into focus |
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As telescopes become larger and larger, astronomers favor ________.
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reflecting telescopes, in part because large lenses and mirrors sag under their own weight, and it is easier to support a mirror along its entire back side than it is to support a lens only around its edge
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What is the resolution of a telescope |
its ability to distinguish two adjacent objects close together in the sky |
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The angular resolution of an 8-inch diameter telescope is ________ better than that of a 2-inch diameter telescope. |
4x |
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One advantage of the Hubble Space telescope over ground based ones is that |
in orbit, it can operate close to its diffraction limit at visible wavelengths. |
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Compared to optical telescopes, radio telescopes are built large because: |
radio photons don't carry much energy. |
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The x of the Hubble Space Telescope is better for shorter (bluer) wavelengths of light than for longer (redder) wavelengths of ligh |
angular resolution |
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xseparate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties. |
SSpectrographs |
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The twin 10-m Keck telescopes can work together to obtain better angular resolution through a technique known as x |
interferometry. |
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The Chandra X-ray observatory focuses X rays with x mirrors. |
grazing incidence |
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A 10-meter telescope has a larger x than a 4-meter telescope. |
light-collecting area |
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In astronomy, an interferometer can be used to |
improve the angular resolution of radio telescopes. |
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What is "seeing"? |
a measurement of the image quality due to air stability |
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In which part of the electromagnetic spectrum have astronomers been unable to get any information? |
We now can access information in all spectral lengths. |
